Formation of staple fiber yarn from nonwoven webs of continuous filaments

ABSTRACT

A staple fiber yarn is formed by laying a nonwoven web of continuous filaments, slitting the web to form strips containing fibers of various lengths, and twisting the fibers together to form the yarn.

ilnite tates Patent Inventors Stanley Davies;

Barrie Linton Davies; Anll Chandrakant Parikh, all of Pontypool, England Appl. No. 816,397 Filed Apr. 15, 1969 Patented Dec.14,1971 Assignee Imperial Chemical Industries Limited London, England Priority Apr. 16, 1968 Great Britain 17,890/68 FORMATION OF STAPLE FIBER YARN FROM NONWOVEN WEBS OF CONTINUOUS FILAMENTS 9 Claims, No Drawings U.S. Cl 156/148, 57/157,156/180 Int. Cl D02g 1/00 [50] Field ofSearch 156/166, 180, 181,271, 148; 57/157 [56] References Cited UNITED STATES PATENTS 3,511,747 5/1970 Davies 156/181 X 2,681,702 6/1954 Kuenn et a1 156/271 X 3,276,937 10/1966 Kim 156/166 X 3,314,840 4/1967 Lloyd et a1 156/181 X FOREIGN PATENTS 974,230 11/1964 Great Britain Primary Examiner-Carl D. Quarforth Assistant ExaminerR. L. Tate A!!orney-Cushman, Darby & Cushman ABSTRACT: A staple fiber yarn is formed by laying a nonwoven web of continuous filaments, s1itting the web to form strips containing fibers of various lengths, and twisting the fibers together to form the yarn.

FORMATION OF STAPLE ER NONWOVEN OF il- The present invention relates to improvements in the formation of yarns of staple fibers and in particular to the formation of staple fiber yarns by slitting fibrous webs.

Processes involving the division of paper sheets of nonwoven webs of aligned staple fibers into narrow strips and twisting the strips to form yarn are known, such processes generally being quicker, simpler and more economical than the more conventional textile processes involving the formation, drafting and spinning of staple fiber slivers to produce yarn. However, the former processes still involve the timeconsuming and complicated steps of either producing the paper sheet or forming the webs of aligned staple fibers.

We have now found that satisfactory yarns can be made from webs of randomly laid continuous filaments and accordingly the invention, in one of its aspects, comprises a process for the production of staple fiber yarns the fibers having various lengths in which a nonwoven web of randomly-laid continuous filaments is divided into strips, the fibers of which are twisted together to form a yarn.

in another, preferred embodiment the fibers of the strips may be twisted together by employing the strips as a feedstock for a break-spinning" device.

By break-spinning assembly we mean apparatus in which a coherent sliver of fibers is broken up into its individual fiber components which are subsequently and continuously reformed into a coherent, twisted yarn which is withdrawn continuously from the apparatus. Such devices have been known in various embodiments for many years and the devices described and claimed in, inter alia, British Pat. specification Nos. 978,958, 974,230, 979,930 and 1,031,150 are examples.

Accordingly the invention comprises, in another of its aspects, a process for making a staple fiber yarn in which a nonwoven web of randomly laid continuous filaments is divided into strips, at least one of said strips being fed to a breakspinning device and withdrawing therefrom a twisted staple fiber yarn.

By randomly-laid filaments we mean filaments laid so that their predominating configuration is random and the webs used on the present invention may comprise filaments laid in a completely random configuration or filaments some of which are partially aligned provided that the predominating configuration is random.

The invention is not limited to the use of any particular kind of continuous filament and the nonwoven webs used in the present invention may for instance by made from synthetic polymeric filaments taken directly from their source, for example a melt spinning head, and laid down by nip rolls or air ejectors on collecting surfaces in a random manner to form a nonwoven web which is then divided into strips which are subsequently twisted and such a process has obvious economic advantages over the processes outlined hereinbefore. When polyamide filaments are used it is preferable to steam the web afier laying down the filaments to stabilize the web before slitting. In an alternative method continuous filaments may be taken from filament packages and laid down to fonn a web.

The webs may be slit, for instance, by using stationary rotary or vibrating knives or, for instance, by using jets of hot air or steam or by using hot wires and the width of strips divided will depend upon the yarn properties required. The fibers of the strips may, for instance, be twisted together on a ringspinning frame and the amount of twist inserted will be dependent on the properties required in the final yarn.

The yarns produced although being derived from continuous filament structure have a staple-yam like appearance since we have found that on dividing the webs into strips some of the randomly arranged continuous filaments are broken and protrude as fiber ends from the final yarn. The properties of the yarns produced depend upon the properties and the position of the continuous filaments in the web, the widths of the strips and the amount of twist put into the yarn and it may be necessary to draw the strips before twisting, or the yarn during or after twisting or both. Such drawing may be necessary to rearrange the filaments in the yarn or to extend any undrawn filaments in the web or to give the final yarn denier required without the necessity for cutting very thin strips.

When the process of the present invention is carried out in a way which does not require the slit web to be broken up into its component fibers, such as when the slit web is twisted by means of a ring spinning device, the filaments may be bonded together if desired either mechanically or adhesively before formation into the yarn. However, when using break-spinning apparatus we have found that bonding before formation of the yarn should be avoided. The yarn when formed by either route may be bonded if desired. Mechanical bonding of the web may be efiected by needle punching and adhesive bonding may be effected by impregnation of the web, strip or yarn with a nonfibrous bonding agent or by the incorporation of binder filaments, for example composite fibers containing a potentially adhesive component, in the webs. The constituent filaments of the web may be crimped or may contain potential crimp which can be developed by appropriate treatment at any desired time during the formation of the yarn and such crimp will generally enhance the handle of the yarn produced.

The invention will now be described in more detail with reference to the following examples which are in no way intended to limit the scope thereof.

EXAMPLE 1 Continuous filaments of poly(hexamethylene adipamide) were extruded through a 40 hole spinneret at 6 lbs/hr. and passed to an air ejector which drew down the filaments by 300 percent and laid down the filaments in a random manner on a foraminous conveyor belt travelling at 2.9 ft./min. to produce a 30-inch wide 2 02./sq.yd. web of 6 d.p.f. filaments. The web was then steamed at atmospheric pressure for 1 minute and slit into 40 sections each three-fourths inch wide which were drawn to 3.5 times their original length and then had 3.5 t.p.i. S twist inserted. The yarn produced from the drawn and twisted strips had a denier of 3,300 and had short fibers produced by the slitting action extending from it giving the yarn staplelike properties.

EXAMPLES 2 This examples illustrates the production of a staple fiber yarn by the process of the invention, using break-spinning apparatus.

A continuous filament web weighing 2 oz./sq.yd. was made by the method described in British Pat. Ser. No. 1,088,931. The filaments were denier core-and-sheath bicomponent filaments having a core of poly(hexamethylene adipamide) and the sheath was a copolymer of 70 percent poly (hexamethylene adipamide) and 30 percent poly(ipsilon caprolactam): the core being 60 percent by weight of the filament.

The web was slit by rotary knives into 1 inch wide strips each having a denier of approximately 20,000 Five of these strips were converged together to make a feed stock of approximately 100,000 denier which was fed to a break-spinning device described in British Pat. Ser. No. 1,03 l ,l50 at a rate of 4.7 feet per minute. The break-spinning device was rotating at 30.000 rpm. The spun yarn was withdrawn at a rate of 200 feet per minute and had a denier of about 2,300, a nominal twist of about 12 turns per inch and had an extension to break of 36 percent.

The yarn was finally passed through an oven and heated to 200 C. whereupon the sheath component of the filaments softened.

On removal from the oven the sheath component solidified fonning bonds between contiguous filaments in the body of the yarn, which then had an extensibility of 22 percent. In appearance the yarn was akin to conventional staple fiber yarns, but could not be unraveled by detwisting.

We claim:

1. A process for the production of a staple fiber yarn the fibers of which are of various lengths comprising slitting a nonwoven web of randomly-laid continuous filaments into strips whereby said strips contain fibers of various lengths and thereafter twisting said fibers together to form a yarn.

2. A process according to claim 1 in which the fibers of the strips are twisted together in a break-spinning device to form a staple fiber yarn.

3. A process according to claim 1 in which the staple fiber yarn is subjected to a drawing or drafting stage.

4. A process according to claim 1 in which the filaments of the nonwoven web are bonded together.

' 5. A process according to claim 1 in which the yarn is subjected to a bonding treatment.

6. A process according to claim 5 in which the filaments are composite filaments having at least two components arranged in distinct zones across the cross section of the filament, at least one component being such that it may be rendered adhesive under conditions which do not sensibly affect the other component, and in which the twisted staple fiber yarn is subjected to a treatment to render adhesive the said component. thereby bonding contiguous filaments in the yarn.

7. A process as in claim 1 including drawing the filaments subsequently to the slitting of the web.

8. A process as in claim 1 wherein the twisting step includes breaking at least one of the strips into its individual fiber components and subsequently and continuously twisting the resulting fiber components to form them into a yarn.

9. A process as in claim 8 wherein the filaments are composite filaments having at least two components arranged in distinct zones across the cross section of the filament, at least one component being such that it may be rendered adhesive under conditions which do not sensibly affect the other component, and in which the twisted staple fiber yarn is subjected to a treatment to render adhesive the said component, thereby bonding contiguous filaments in the yarn. 

2. A process according to claim 1 in which the fibers of the strips are twisted together in a break-spinning device to form a staple fiber yarn.
 3. A process according to claim 1 in which the staple fiber yarn is subjected to a drawing or drafting stage.
 4. A process according to claim 1 in which the filaments of the nonwoven web are bonded together.
 5. A process according to claim 1 in which the yarn is subjected to a bonding treatment.
 6. A process according to claim 5 in which the filaments are composite filaments having at least two components arranged in distinct zones across the cross section of the filament, at least one component being such that it may be rendered adhesive under conditions which do not sensibly affect the other component, and in which the twisted staple fiber yarn is subjected to a treatment to render adhesive the said component, thereby bonding contiguous filaments in the yarn.
 7. A process as in claim 1 including drawing the filaments subsequently to the slitting of the web.
 8. A process as in claim 1 wherein the twisting step includes breaking at least one of the strips into its individual fiber components and subsequently and continuously twisting the resulting fiber components to form them into a yarn.
 9. A process as in claim 8 wherein the filaments are composite filaments having at least two components arranged in distinct zones across the cross section of the filament, at least one component being such that it may be rendered adhesive under conditions which do not sensibly affect the other component, and in which the twisted staple fiber yarn is subjected to a treatment to render adhesive the said component, thereby bonding contiguous filaments in the yarn. 